The soybean has been utilized for thousands of years as a source of both oil and protein. It is currently one of the most important agricultural sources of these important products, which are used for both animal and human consumption. In addition, with the growing concern over the long term supply of petroleum products, many industrial uses for soybean oil are developing. While other methods exist, soybean oil is typically isolated from the solids by extraction with an organic solvent. The soybean product that remains after extraction of the oil can be either desolventized and toasted, to form a defatted toasted soy meal, for use in an animal feed, or flash desolventized to form an intermediate product, referred to as “white flakes”, that is further processed for use in food and nutritional products, e.g., tofu and soy protein isolate.
A raw soybean consists of an outer covering, referred to as the hull; two bean halves, referred to as the meat or cotyledon; and an embryo, referred to as the germ or hypocotyl. In conventional soybean processing, the hulls are often removed, to facilitate oil extraction and to reduce the amount of fiber in the soy meal. In typical soybean processing the oil and the solvent laden white flakes are produced from a mixture of meats (>90% by weight), germ (about 2%), and a small residual percentage of hulls. Further purification of the oil and solvent laden white flakes results in commercially suitable products.
A conventional process for forming soybean oil and solvent laden white flakes from soybeans is shown in FIG. 1. According to this process, soybeans are dried to a moisture content of about 9–11%, tempered for approximately 24–72 hours, and passed through two sets of cracking rolls, to crack the soybean meats into quarters and eighths (i.e., a large portion of the meats are in quarter or eighth size pieces) which causes the hulls to separate from the meats. Most of the hulls are then removed by a series of aspirating and sifting steps. The remaining cracked soybeans are then conditioned (heated to soften them), flaked to facilitate oil extraction, and extracted using a solvent such as hexane. This process results in three products: crude soybean oil, hulls, and solvent laden white flakes. Since solvent laden white flakes are not a commercial product, they need to be further processed by solvent removal and/or toasting desolventizing. In the process shown in FIG. 1, some of the germ is processed with the meats, and some may be unintentionally aspirated off with the hulls.
Recently, the medical and nutrition community have become aware that soy germ contains a relatively higher concentration of nutrients (e.g., isoflavones, tocopherols and sterols) than the meat. Thus, efforts have been made to separate a very pure (>90%) soy germ fraction from a soybean stream, e.g., as described in WO 96/10341 and U.S. Pat. No. 5,952,230. These references, however, do not describe how the separation of soy germ from soybeans would be successfully integrated into a process for producing soybean oil and low fiber solvent laden white flakes.